Assessments of stock losses and flood damage suffered by farmers in the Lower Buller Gorge, Inangahua, Reefton, Shenandoah and Maruia are underway.
Federated Farmers West Coast president Bede O'Connor estimated at least 30-40 farms had been significantly damaged by a combination of flooding and slips. Others suffered when streams, tracks and culverts blew out.
For some farmers it was the second time in seven months they had lost roads, tracks, fences and feed, and had their paddocks covered in silt, O'Connor said.
Farms on both sides of the lower reaches of the Buller River were not as badly affected as last July, but heavy silting covered paddocks in the Nine Mile and on land beside the river.
Farmers everywhere were reporting extensive damage to farm infrastructure, particularly in and around the Inangahua and Reefton area, O'Connor said.
"As far as we know there have not been any major stock losses, but I would not be surprised if there had been some - the speed the river rose was amazing."
After six days of being cut off because of slips and dropouts on the Karamea Bluff road, dairy farmers were finally able to truck their milk out, convoys of vehicles being allowed to cross the damaged hill road three times a day.
O'Connor said he understood most farmers in that area had not been badly affected by flooding. However, those between Westport and Mokihinui had suffered badly.
He was wary of attributing the flooding to climate change, saying instances of two big floods hitting the region within six months had happened before.
The flooding events were also quite different, with heavy rain falling on parched summer soil and last week's being driven by very heavy rain, he said.
Still, the two events were likely to have already resulted in changes to farming operations, particularly by those near the river.
Flood-prone riverside land made up a large amount of the good farming land on the West Coast, he said.
"For farmers who have been hit twice by flooding it is hard. But we are in a record payout year.
"It's disappointing, the increase will be down because of the flood damage but it could be worse."
Federated Farmers was working with the Rural Support Trust to offer support.
"If the sun comes out for a few days, people will be out getting things fixed."